Ideas of neighborhood and community animate the study of the American city. Urban Lowlands is a comparative history of four low-lying neighborhoods: Harlem Flats in New York City; Black Bottom in Nashville; Swede Hollow in Saint Paul; and the Flats in Los Angeles. Physical processes of infrastructural development and city building, natural processes of hydrology and geology, and social and political processes of stigmatization and municipal neglect combined to create urban lowland neighborhoods. Known as bottoms, hollows, and flats, they were a common feature of the American urban landscape between 1870 and 1940. The book presents an alternative conceptual framework for studying environment and poverty in the United States, arguing that water problems, disease fears, and attitudes about race, ethnicity, and class strongly influenced modern city planning. It delves into the material and social processes of the construction of the urban landscape, including professional discourses in public health and housing reform, vernacular speech, journalism, and politics. Lowland residents encountered social marginalization and environmental hazards as they struggled for better lives and better communities. Elected officials and professional experts debated whether to contain poor and working-class people where they lived or forcibly evict and disperse them. Public health officers, engineers, business leaders, housing inspectors, and planners framed bottoms, hollows, and flats as threats to the entire city. Municipal debates over slum clearance in urban lowland neighborhoods shaped zoning, redlining, highway building, and public housing programs. The material and ecological implications of these decisions continued into the early twenty-first century.